Control circuit



Feb. 2, 19 3 o. A. FIEARSON CONTROL CIRCUIT Filed April 50. 1941 050mm? Pea/502a Patented Feb 2, 1943 lTED stares Pair CONTROL CIRCUIT Oscar A. Pearson, Oak Park, IlL, assignor to Jefi'erson Electric Company, Bellwood, lit, a corporation oi Hlincis Application April 30, 1941, Serial No. 391,168

3 Claims.

This invention relates to control circuits, and more particularly to circuits providing safety from shocks and short circuits. I

There are circuits in common use which subjectinexprienced people to danger of shocks and the electrical apparatus used to damage from short circuits. The adaptation of the particular circuits disclosed herein is to lighting with gas discharge tubes requiring relatively high operating potentials.

It is an object of this invention to provide an electrical control circuit which is automatically de-energized upon the occurrence of an abnormal condition and which requires deliberate resetting for re-energization.

Another object of this invention is to provide an electrical control circuit which becomes automatically de-energized upon the occurrence of an open circuit and remains normally de-energized during the existence of the open circuit and until deliberately reenergized.

Another object of this invention is to provide a lighting control circuit including a lighting unit, a transformer through which operating potential is applied to the'lighting unit, and means for opening the primary circuit of the transformer if and when the secondary winding circuit is opened.

Another object of this invention is to provide a control circuit including a transformer and an electromagnetic switch having a'holdin'g coil con nected in the circuit of the transformer secondary winding for holding the switch closed and a circuit closing element connected in series with the transformer primary winding.

Anotherjobject of this invention is to provide acontrol circuit including a transformer, an electromagnetically actuated switch having a holding coil connected in the secondary winding circuit of th transformer for holding the switch closed and automatic means for preventing the 'reclosin of the primary circuit of the transformer for a predetermined length of time after it has been opened. V I

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodimentiof the present invention is clearly shown.

In the drawing: Figure l is a schematic circuit diagram of a control circuit embodying a preferred form of the present invention; and V a I Figure 2 is a schematic circuit diagram illus-, trating a modification of the invention.

Referring to Figure 1, a transformer ID ha a core 12, a primary winding l3 and a secondary winding which is preferably divided into halves i4 and l5.' One side of the primary winding I3 is connected to a power supply line lead I6 plied to the gas discharge tube electrode.

through a main line circuit control switch H. The other side of the primary winding is connected to a power supplyline lead I8 through contacts l9 and and a contact bridging element 22 of a switch 23. The switch 23 is normally biased to the open circuit position by a spring or other suitable means 24 and is actuated to the closed position by a manually operable operating member-or-push button 25.

One end of the half ll of the secondary winding is connected to ground at 26. The other end of that half of the secondary winding is connected to an electrode 21 of a gas discharge tube 28. One end of the half I5 of the secondary winding is connected .to an electrode 29 of the gas discharge tube 28. The other end of the half i5 of the secondary winding is connected to ground at 30 through a solenoid or electromagnet winding 32 which preferably has low impedance. The halves M and i5 of the secondary winding are wound and connected so that their potentials are additive and their combined voltage is ap- The ends of the halves of the secondary winding which are connected to'ground at 26 and 30 preferably comprise the mid-point of the winding.'

A core 33 of magnetic material is magnetically asssociated with the electromagnet winding 32 and is secured to the contact bridging element 22 I to hold theswitch 23 in the circuit closing position against the biasing force of the spring 24 after the switch is actuated to the closed posinormal current tion and during the flow of through the winding 32.

' In theoperation of the circuit-shown in Figs ure 1, the main line control switch I! is actuated manually or otherwise, but does not complete the circuit f-romthe power supply line leads I6 and IE to the primary winding 13 until the switch 23 is manually closed. -'I'he actuation of both of the switches I! and 23 is necessary to the completion of the power supply circuit to the primary,

winding. When the switch 23 is actuated to the closed position after the closing of the switch H,

the secondary winding potential is app-lied to the electrodes 21 and 29 of the gas discharge tube 28 to eiiect a discharge within that tube and a'consequentcurr'ent flow throughv the ga discharge tube and 'the'halves of thesecondary winding.

This current flow under normal operating conditions energizes the electromagnetj winding 32 which is connected in series with the half [I5 of the secondary winding, and thereby holds the switch 23 in the circuit closing position. -Upon th interruptionof the current flow through the secondary winding circuit, as by the failure or breaking of the gas discharge tube 28 or the breal;ing of a lead theretofthe electromagnet winding 32' is de-energized and the switch 23 is opened by the biasing force of the spring 24. The opening of the switch 23 opens the circuit to the primary winding 13, which circuit remains open until manually reclosed.

magnet actuating winding 38 of the switch 31 is 1 connected to the power supply 'line lead i3 through a norm ally closed temperature responsive switch 39 which preferably has a bimetallic ele ment 40 connected in the circuit between the power supply line lead I and the actuating winding 38. The bimetallic element 48 has one end anchored at 42 and the other end free to flex to open the circuit to the actuating winding.

The other end of the actuating winding 38 is connected to the power supply line lead l8 through the main line control switch II. A resistance heating element 43 is closely associated with the bimetallic element 40 to insure heating of the element, and is connected directly to the power supply line lead it and to the power supply line lead l8 through the switch l1. The switch 31 has a movable magnetic core 44 connected to the contact bridging element 38 and adapted to be actuated by the actuating winding 38. This switch also has a holding winding 45 which is connected in series with, and between the halves i4 and ii of the secondary winding.

In the operation of the circuit shown in Figure 2, the closing of the main linecontrol switch l1 normally closes a circuit from the power supply line leads l3 and II to the actuating electromagnet winding 38 through the bimetallic temperature responsive switch 38. At the same time a circuit is closed from the power supply line leads l6 and I8 to the resistance heating element 43. The actuating electromagnet winding 33 effects closure of the switch 31 to close the circuit from the power supply line leads to the primary winding II of the transformer. The energization of the transformer secondary winding com p'zsing the halves i4 and i provides operat ng potential for the gas discharge tube 28. Upon the commencement of the discharge within the ing circuit results in the opening of the switch 31 by the biasing spring 4|. The operation of the circuit cannot then be re-established until after the switch I] has been opened for a period of time suiiicient to allow the heating element 43 and bimetallic element 48 to cool and re-establish the engagement of the contacts of the switch 33 and until the switch i1 is again manually closed.

While the embodiment of the present invention as herein disclosed. constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

of the secondary winding having center and heater terminals, said illuminating device being "1 iconnected to the outer terminals, two switches being connected in series with the power supply line and primary winding, both of said switches being manually operable to the closed position andone of the switches being normally biased to 'the open position and having electromagnetic tube 23, current flow through the-secondary winding and the holding winding 45, which is cdnnected in series therewith, energizes that holding winding to maintain the switch 31 in the closed position during the normal operation of the gas discharge tube.

The heating of the resistance heating element '43 which follows the closing of the switch l1 transfers heat to the bimetallic element 48 to eifectfiexure of that bimetallic element and the opening of the circuit to the actuating electromagnet winding 38 through the contacts of the switch 33. As long as the switch l1 remains closed, the resistance heating element 43 remains heated and maintains the bimetallic element 40 in a fiexedposition. A period of time is required for the bimetallic element to return to the circuit closing position after the opening of the switch l1. As a consequence, during normal operation, only the holding winding 45 maintains theswitch 31 in the closed position, and any abnormal condition which interrupts the current flow through the gas discharge tube 23 or the secondary windholding means for holding the switch closed, the center terminals of the secondary windings being grounded, and at least one of the ground connections to the center terminals of the secondary windings being made through said electromagnetic holding means.

2. A control circuit for high voltage illuminating systems comprising,.in combination, a gas discharge illuminating device, a power supply line, a transformer having primary and secondary windings, the primary winding being connected to the power supply line through a main line control switch and an auxiliary switch, the secondary winding being divided into halves and providing potential for operating the illuminating device, said auxiliary switch including electromagnetic switch operating means andelectromagnetic switch holding means for holding the switch closed, a temperature responsive switch having a heating element, said heating element being connected to the power supply line through the main line control switch, said electromagnetic switch operating means being connected to the power supply line through the main line control switch and the temperature responsive switch, and said electromagnetic switch holding means being connected in series with the halves of the secondary winding.

3. A control circuit for illuminating systems comprising, in combination, a power supply line. an illuminating device, a plurality of switches in series with the power supply line which must each be closed for providing potential for the operation of the illuminating device, one of said switches being manually operable, electromagnetic means for operating another of the switches, temperature responsive switch means for controlling the operation of the electromagnetic means, and rendering the electromagnetic means ineffective during normal operation of the liluminating device, and holding means effective during normal operation of the illuminating device for retaining the electromagnetically operated switch closed during normal operation of the illuminating device.

OSCAR A. PEARSON. 

